Light reflections from reflective surfaces, such as for example glossy paper, electronic tablets, or wet road surfaces, may be disturbing and glaring for an observer such as a reader of a text or a driver of a vehicle.
In for example U.S. Pat. No. 3,566,099, this issue is addressed by providing a light projection assembly having a polarizer arranged over the mouth of a parabolic reflector such that light passing through the polarizer is linearly polarized.
The amount of light that is reflected towards the eye of the observer may e.g. depend on the direction of polarization of the incident light, and the plane of incidence. The plane of incidence can be defined by a gaze point of the observer viewing the surface, a position of the light source and the at least partially reflective surface. By illuminating a reflective surface with light having a direction of polarization parallel to the plane of incidence, especially at an angle of incidence close to the Brewster angle, the extent of light reflection from the surface may be reduced.
There is however still a need for an improved illumination device enabling an improved control of the extent of light reflection from illuminated surfaces.
U.S. Pat. No. 2,402,176 discloses a device for the illumination of surfaces and is directed more particularly to the modification of light impinging on or reflected from surfaces in such manner as to eliminate or minimize glare when said surfaces are viewed by the human eye.
U.S. Pat. No. 5,161,879 discloses a flashlight for security personnel which has a gravity actuated switch for application of electrical power to multiple lamps to enable the projection of light in downward directions to illuminate multicolored working surfaces and to inhibit the projection of light in horizontal and other directions where hostile persons may be watching. The projected light intensity is variable by polarizing optical means and is coordinated with the gravity switch and the user's control so that the initial intensity at turn-on of the flashlight occurs at the lowest projected intensity.
US2002/0113560 discloses a lighting apparatus having a linearly polarizing lens. The polarizing lens is rotatable to any position in between a first position and a second position. By rotating the polarizing lens, different planes of polarization can be achieved. A user can also choose to vary the amount of rejection of surface reflectance by selectively adjusting the polarizers intermediate their first and second predetermined positions.